/*
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you under the Apache License, Version 2.0 (the
 * "License"); you may not use this file except in compliance
 * with the License.  You may obtain a copy of the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package org.apache.flink.runtime.util;

import org.apache.flink.core.fs.FSDataOutputStream;
import org.apache.flink.core.testutils.OneShotLatch;
import org.apache.flink.runtime.state.CheckpointStreamFactory;
import org.apache.flink.runtime.state.StreamStateHandle;
import org.apache.flink.util.IOUtils;

import javax.annotation.Nullable;

import java.io.IOException;
import java.util.concurrent.atomic.AtomicBoolean;

/**
 /**
 * This test utility class provides a CheckpointStateOutputStream (which is also a FSDataOutputStream) that can block
 * on a latch and takes a latch that the creator can block on until the stream is closed. This is typically used to
 * test that a blocking read can be interrupted / closed.
 */
public class BlockingCheckpointOutputStream extends CheckpointStreamFactory.CheckpointStateOutputStream {

	/** Optional delegate stream to which all ops are forwarded. */
	private final FSDataOutputStream delegate;

	/** Optional latch on which the stream blocks, e.g. until the test triggers it after some call to #close(). */
	private final OneShotLatch triggerUnblock;

	/** Optional latch on which the test can block until the stream is blocked at the desired blocking position. */
	private final OneShotLatch waitForBlocking;

	/** Closed flag. */
	private final AtomicBoolean closed;

	/** The read position at which this will block. 0 by default. */
	private final long blockAtPosition;

	/** The current read position. */
	private long position;

	public BlockingCheckpointOutputStream(
		@Nullable OneShotLatch waitForBlocking,
		@Nullable OneShotLatch triggerUnblock) {
		this(null, waitForBlocking, triggerUnblock, 0L);
	}

	public BlockingCheckpointOutputStream(
		@Nullable FSDataOutputStream delegate,
		@Nullable OneShotLatch waitForBlock,
		@Nullable OneShotLatch triggerUnblock) {
		this(delegate, waitForBlock, triggerUnblock, 0L);
	}

	public BlockingCheckpointOutputStream(
		@Nullable FSDataOutputStream delegate,
		@Nullable OneShotLatch waitForBlocking,
		@Nullable OneShotLatch triggerUnblock,
		long blockAtPosition) {

		this.delegate = delegate;
		this.triggerUnblock = triggerUnblock;
		this.waitForBlocking = waitForBlocking;
		this.blockAtPosition = blockAtPosition;
		if (delegate != null) {
			try {
				this.position = delegate.getPos();
			} catch (IOException e) {
				throw new RuntimeException(e);
			}
		} else {
			this.position = 0;
		}
		this.closed = new AtomicBoolean(false);
	}

	@Override
	public void write(int b) throws IOException {

		if (position == blockAtPosition) {
			unblockWaiter();
			awaitUnblocker();
		}

		if (delegate != null) {
			try {
				delegate.write(b);
			} catch (IOException ex) {
				unblockWaiter();
				throw ex;
			}
		}

		// We also check for close here, in case the underlying stream does not do this
		if (closed.get()) {
			throw new IOException("Stream closed.");
		}

		++position;
	}

	//We override this to ensure that writes go through the blocking #write(int) method!
	@Override
	public void write(byte[] b, int off, int len) throws IOException {
		for (int i = 0; i < len; i++) {
			write(b[off + i]);
		}
	}

	@Override
	public long getPos() throws IOException {
		return position;
	}

	@Override
	public void flush() throws IOException {
		if (delegate != null) {
			delegate.flush();
		}
	}

	@Override
	public void sync() throws IOException {
		if (delegate != null) {
			delegate.sync();
		}
	}

	@Override
	public void close() {
		if (closed.compareAndSet(false, true)) {
			if (delegate != null) {
				IOUtils.closeQuietly(delegate);
			}
			// trigger all the latches, essentially all blocking ops on the stream should resume after close.
			unblockAll();
		}
	}

	private void unblockWaiter() {
		if (null != waitForBlocking) {
			waitForBlocking.trigger();
		}
	}

	private void awaitUnblocker() {
		if (null != triggerUnblock) {
			try {
				triggerUnblock.await();
			} catch (InterruptedException ignored) {
			}
		}
	}

	private void unblockAll() {
		if (null != waitForBlocking) {
			waitForBlocking.trigger();
		}
		if (null != triggerUnblock) {
			triggerUnblock.trigger();
		}
	}

	@Nullable
	@Override
	public StreamStateHandle closeAndGetHandle() throws IOException {

		if (!closed.compareAndSet(false, true)) {
			throw new IOException("Stream was already closed!");
		}

		if (delegate instanceof CheckpointStreamFactory.CheckpointStateOutputStream) {
			StreamStateHandle streamStateHandle =
				((CheckpointStreamFactory.CheckpointStateOutputStream) delegate).closeAndGetHandle();
			unblockAll();
			return streamStateHandle;
		} else {
			unblockAll();
			throw new IOException("Delegate is not a CheckpointStateOutputStream!");
		}
	}

	public boolean isClosed() {
		return closed.get();
	}
}
